1. Field of the Invention
The present invention relates to a powder catalyst supply apparatus and a catalyst supply system and, more particularly, to a powder catalyst supply apparatus and a catalyst supply system which are suitable for olefin gas phase polymerization reaction.
2. Related Background Art
In an apparatus for manufacturing a polyolefin by using an olefin gas phase polymerization reaction vessel, a powder catalyst must be supplied to the reaction vessel. It is preferable that this powder catalyst be continuously supplied. In reality, however, there is no apparatus that can continuously and constantly supply granulated powder particles into a gas phase polymerization reaction vessel at a high pressure. As disclosed in Japanese Patent Publication No. 49-17426 and Japanese Patent Laid-Open No. 60-227824, a batch metering/supplying system is generally employed, in which a catalyst is metered by a metering pipe, and is supplied by using an inert gas as a carrier gas. An example of the batch metering/supplying system will be described below with reference to FIG. 1.
A powder catalyst is supplied from a catalyst storage hopper 2 to a gas phase polymerization reaction vessel 1 by using an olefin gas or an inert gas as a carrier gas, and a polymerization reaction is caused, thereby manufacturing a polyolefin. In this catalyst supply method, in order to prevent solidification of powder particles, which is caused when an olefin gas enters the catalyst storage hopper 2, a batch supply system using a metering pipe 3 is employed. More specifically, a valve 8 is opened while the valves 4, 5, and 6 are closed, so as to fill a volume tank 7 with an inert gas which does not contribute to a reaction. Thereafter, the valve 8 is closed, and the valve 4 is opened to inject a catalyst from the catalyst storage hopper 2 into the metering pipe 3. The valve 4 is then closed, and the valves 5 and 6 are opened to supply the catalyst in the metering pipe 3 into a catalyst supply pipe 9, by using a pressurized gas from the volume tank 7. The catalyst supplied to the catalyst supply pipe 9 is supplied to the gas phase polymerization reaction vessel 1 together with the olefin gas flowing in the catalyst supply pipe 9. By repeating this operation, entrance of the olefin gas into the catalyst storage hopper 2 can be prevented, and the catalyst can be supplied to the gas phase polymerization reaction vessel 1 at a high pressure. In the gas phase polymerization reaction vessel 1, the supplied catalyst speeds up a polymerization reaction, thus manufacturing a polyolefin.
In addition, Japanese Patent Publication No. 53-8666 discloses an apparatus which is constituted by a metering means having a rotating shaft member and is designed to inject granular particles into a reaction chamber. In this apparatus, granular particles are supplied from the metering means to the reaction chamber through a capillary tube having an inner diameter of 0.76 to 3.2 mm. For this reason, when granular particles are to be supplied in a large amount, the capillary tube may clog up, and hence it is difficult to stably supply granular particles to a reaction vessel of an industrial scale.
In the conventional system, although entrance of an olefin gas into the catalyst storage hopper 2 and solidification of a catalyst upon polymerization can be prevented, the catalyst is intermittently supplied from the catalyst storage hopper 2 to the catalyst supply pipe 9. For this reason, the catalyst is intermittently supplied to the gas phase polymerization reaction vessel 1 to interfere with uniform distribution of the catalyst in the gas phase polymerization reaction vessel 1. As a result, a dense catalytic portion is formed to generate a lump upon local polymerization, and a mixing failure is caused in the reaction vessel 1, increasing the possibility of clogging up the reaction vessel 1. In addition, the manufacture of uniform products is adversely affected. It is considered that the period at which the catalyst is intermittently supplied may be shortened by reducing the capacity of the metering pipe 3. In this case, however, the frequency of opening/closing operations of the valves is increased to shorten the service life of the apparatus.